ETX TECHNICAL TIPS
My Suburban Refuge from Lights, Wind, Skunks and Nosey Neighbors
"It don't get any better'n this....." Those words from the beer commercial conjure up images of tree frogs beginning their melodies as the sun goes down, afternoon winds waning into warm summer breezes of night....dark skies and remote locations.
They also describe my "ETX Heaven," a 10-foot by 10-foot observing deck and privacy area in which my ETX takes me to explore strange new worlds, to seek out new adventure and to go where no man has gone before....
An hour from my home, atop Petit Jean Mountain is my dark sky location at an elevation of a "straight up" 1,000 feet over the Arkansas River valley. There are not street lights, no neighbors, no car headlights going by.....
....but that is an hour from my home. Having a family I still DO spend a lot of time at "home" contrary to what a lot of people think, but my mind is still wandering all the while to "astronomy" and viewing some new comet or cataclysmic variable. For that I have my ETX 125, my portable GO-TO, GO-EVERYWHERE scope that packs a lot of punch into a small "Mighty ETX" pouch.
I have found myself using the ETX 125 more and more and the large telescopes less and less. Yet, like all of us, my suburban home in Conway, Arkansas is plagued with streetlights, heavy traffic, curious neighbors and - yes - even an occasional skunk or two that wanders in from the woods surrounding the Arkansas River valley only a walk away.
Since I have had my ETX 125 - a heavily modified and "beefed" model that can put a "tractor pull" competition to shame - I have shared its fabulous observing time between the mountain and here in Conway, but the conditions at home are such that the city has grown my way dramatically just in the last two years. Hence, the street lights have become overwhelming and I knew that I must do something if I was to continue any degree of serious observing from my home.
An observatory was out of the question because of our neighborhood restrictions and would be a bit of overkill anyway for the ETX 125 since I like the "great outdoors" when observing with the big, open sky ahead of me.
FITTING RIGHT IN
Our home has an acre lot and a huge wrap-around veranda-style deck across the back where I have done much observing in spite of the serious vibrations from walking around on the wooden surface while observing; it has sufficed for casual observing until the lights moved in on me.
The city fathers of Conway have cooperated with me and installed "light block" shields on virtually every street light that shines directly into my back yard. I have found that if you approach the city intelligently and explain your "avocation" to them and the fact that the lights are intruding into your property...they WILL listen; mine were covered up within a week of my request!
Because our home is only three years old, the sky is wide open and excellent for unobstructed viewing; but there are distant (and near) bothersome lights from throughout western Conway that still presented many problems in observing faint objects.
In addition, we have very high wind gusts from a large bend in the Arkansas River that funnel directly up the highway that passes from the river right by our property; these gusts can not only be bothersome, but they can outright knock a guy's telescope over!
So my plans to construct a permanent observing station for my custom made pier and ETX 125 included all of these facets and was designed along the "look" of the existing veranda and in such a way that all lights and wind - and stray skunks and neighbors - were totally blocked OUT from within the 10-foot-square observing station. The two photographs in Figure 1 show a view of the new observing station the day it was completed (it has since been landscaped and the construction debris has been removed). Note how I merely opened up the south end of the veranda, added a suspended walkway and connected the observing area with the wide-open deck. This makes for a wonderful entertaining area as well now, since a barbecue pit, outdoor speakers and comfort areas merely invite even more hands-on company entertainment as guests can now observe Saturn while consuming one of Clay's world-famous burgers.
The walls of the observing deck are cedar fence slats, 6-feet high which is ideal for the 52" pier height and also for blocking troublesome lights from nearby churches and one busy intersection. It also reduced the wind trouble nearly 100 percent. In Figure 2, you can see the suspended walkway leading into the enclosed ETX Deck; note that the 2 x 4 lumber deck flooring has been sealed beneath to prevent moisture (and mosquitoes) from rising up from the moist ground into the telescope area.
The custom pier (see a complete description under Tech Tips/ An ETX 125 Custom Pier on the Mighty ETX Site) remains outside, covered with a small waterproof tarp and secured when not in use; the telescope, of course - all 20 pounds of it - merely comes indoors when observing is complete.
Note the large antique sundial in this photograph. This device is used to very accurately determine local time when initializing my AutoStar to observe satellite passages. And....if you believe that.....
Figure 3 demonstrates the ETX 125 in its polar position within the ETX Deck on its pier and wedge. Note that every corner has a small corner "table." This is a must for eyeglasses, eyepieces, coffee cups, charts....you really lose sight of how much JUNK we take out observing with us until you need a place to put all of it!
In Figure 4, we see yet another corner table, this one with the only light in the ETX Deck; it is equipped with an outdoor safety switch (just to the right) and a Wratten #25 red filter encompassing a 15-watt bulb for observing comfort. The light is VERY handy when it comes to initialization and first alignment of the evening; it also assists in take-down at the end of observing sessions.
FULLY EQUIPPED -
In Figure 3 you can see three "boxes" on the floor; each pier leg is firmly bolted to 300 pounds of concrete via one of three columns (4" PVC pipe filled with concrete and going into the main concrete pier below the deck). A 3/8" bolt extrudes out of the surface of each pipe (painted black and equipped with red LED lights to prevent tripping) on which the pier is attached. Vibrations dampen in this arrangement within two to three seconds when the pier is rapped strongly.
Each of the "boxes" serves as a trim and seal through which the PVC supports come UP through the deck but DO NOT TOUCH the deck. That way, the telescope pier is entirely independent of the ETX Deck; no matter how much you stomp around on the floor, the telescope image remains solid and stable.
The pier was level accurately during construction and the wedge has been fully aligned permanently with the North Celestial Pole using the "Kochab Clock" method as described in Part 5 of the ETX Enhancement Series on this site. The telescope will track on this pier for as long as you like at over 400 magnification without any drift in declination. I merely slip the telescope and its fork mount into one slotted access hole at the top of the tilted wedge plate, do an "Easy" two-star Polar alignment and I am observing within four minutes.
Electricity is provided throughout the ETX Deck; each corner table has power, as does the suspended walkway in case a small fan during hot summer nights might be used. Power is routed below the deck to the main pier where electrical receptacles remain live for the AC/DC converter to operate the telescope, the pier leg lights and any other accessories.
This project is something that all ETX and LX users should consider....it's cheap, practical, and practically invites you to observe each evening, offering seclusion, darkness, warmth and the occasional tree frog croaking in the creek nearby.
My total investment (I did all the work and construction myself and obtained the lumber through the observatory wholesale) was less than $300 (not including the telescope!) and it took only about two weeks of spare time to complete.
Such a little refuge, away from the hustle and bustle of the busy street and the lights of suburbia USA, is much akin to therapy where all your worries and cares are quickly focused far away to some distant galaxy....
...."it don't get any better'n this."
P. Clay Sherrod
Arkansas Sky Observatory
Conway / Petit Jean Mountain
The pier was designed and built in January prior to plans for the observing station so I needed to accommodate the three legs and feet when the deck was designed.
I have received a lot of questions and generated some interest in construction of similar platforms by other ETX users and I believe that the sub-floor construction is every bit as vital (if not more so) than the "cosmetic" part that we and our neighbors have to look at ( ".....oh, I see you built a 'fort' for you grandkids!"......my quick explanation, and one that is MUCH more acceptable than "observatory" is "hot tub enclosure; they actually buy that, no questions asked and no strange empty stares!).
This figure demonstrates the subflooring as it is being installed; notice that the arrow in the rear is pointing to the southwest 4" PVC column that will be filled with concrete; this pipe has been anchored into a 2-foot slab of cement that holds two other similar columns at 120 degrees separation, each supporting ONE foot of the pier. Vital to proper support are the following points that should be incorporated into ANT observing structure:
1) stability - you must have something that does not shake from touch, nor from a gravel truck barreling down the highway nearby;
2) support - the substructure for any pier must take into consideration the DESIGN of the pier and the "load" on top of it; for example, the ETX or LX scopes "lean" northward in Polar Position and the center of gravity should be considered;
3) isolation - the firm and heavy substructure MUST be totally isolated from the surface on which you walk! Every footstep is a troublesome vibration seen under any magnification if it is not properly separated from the floor!
The entire pier is supported via one large sub-earth block of cement that is 45" square and extends two feet below the ground surface; this IS below the frost line, but this is not necessary for two reasons:
1) Using heavy PVC pipe (6.5" diameter) for the pier will not result in moisture and/or temperature transfers from the ground upward;
2) The entire pier and its surrounding deck is elevated almost exactly two feet ABOVE ground level, allowing for ample ambient air circulation for winter and (very useful for) summer months.
This photograph (of the NORTH leg support) shows clearly the effort that was made to separate ENTIRELY each leg from the support sub-floor structure. Each leg extends from the concrete slab (below the gravel seen on the ground) about 2 feet upward and was leveled precisely using the concrete block ("A" with arrow in photo) placed over each leg and into the wet cement slab during the curing process; once leveled, the block itself was filled with cement for stability and vibration dampening.
To further increase stability and reduced vertical vibrations prone to an extended cylinder such as each leg support, I added 2 x 2 treated lumber braces ("B" in the photo) that inter-connect all three pipes for each leg. NOTE that the 2 x 2 brace substantially reduces any remaining vibration, and MUST be placed well enough below where the final floor will be to assure no contact between the floor and the brace!
Regarding the isolation of each leg from the floor, note two factors in the last photograph:
1) each leg is totally isolated from the subflooring as shown, with a "box" constructed around it for floor support; at no point does any lumber reach within 2" of any pipe support, thus assuring no vibration from the floor whatsoever; the decking 2 x 4 treated lumber likewise is kept away from the leg supports by the same distance.
2) each PVC 4" pipe was extended to reach two inches (2") ABOVE the final deck floor, elevating the point of contact between the pier legs and the top of the column for a reason: I would prefer to have my toe (or the toes of others) stumped on the PVC pipe filled with cement than on the metal pier leg and cause a possible loss of precise polar alignment! Toes are "cheap" compared to good polar alignment!
During the curing process - before the overall slab of concrete is allowed to firmly set - I filled each of the 4" PVC with remaining cement to the top of each pipe as can be seen in the lower photograph. The two REAR supports were fitted with 3/8" extruding bolts that were 8" in length with two very large fender washers and nuts embedded deep into the cement to anchor; the front (NORTH, shown) leg support was left without a stud for alignment purposes. Once precise alignment was achieved, I merely drilled into the cement with a concrete bit (1/2") slipped in a lead anchor at the appropriate spot for a precise alignment (determined over the previous week) and secured the north leg to its support via a 3" lag bolt.
The exposure caps of the PVC and filling cement were painted a satin black to match the ETX black of the telescope.
We have not had a barn dance in the "Stairway to Heaven" yet, nor have my grandkids had a chance to play "fort" in it while I observe. Nonetheless, I HAVE had six people at a time walking and moving about while others observed Saturn and the companion to Castor at about 310x with absolutely NO vibration being see from our presence.
My "Stairway to Heaven" is truly a very solid stepway indeed!
P. Clay Sherrod
Arkansas Sky Observatory
Conway / Petit Jean Mountain, Arkansas
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